Submarines in the Soviet Navy were developed by numbered "projects,"
which sometimes but not always were given names. During the
Cold War, NATO nations referred to these classes by
NATO reporting names, based on intelligence data,
which did not always correspond perfectly with the projects. See:
The NATO reporting names were based on the British (and later American) habit of naming submarines with a letter of the alphabet indicating the class, followed by a serial number of that class. The names are the radiotelphonic alphabet call sign of a letter of the alphabet. For security purposes, the "pennant numbers" of Soviet submarines were not sequential, any more than those of Soviet surface vessels were.
Most Russian (and Soviet) submarines had no "personal" name, but were only known by a number, prefixed by letters identifying the boat's type at a higher level than her class. Those letters included:
К (K) — крейсерская (kreyserskaya, "cruiser")
ТК (TK) — тяжелая крейсерская (tyazholaya kreyserskaya, "heavy cruiser")
Б (B) — большая (bolshaya, "large")
С (S) — средняя (srednyaja, "medium")
М (M) — малая (malaya, "small")
Any of those prefixes could have С (S) added to the end, standing for специальная (spetsialnaya) and meaning "designed for special missions."
